Automatic transmission torque converters are often equipped with a clutch to rotatively link a torque converter turbine with a torque converter input shell, i.e. a clutch drive element. Engagement of a clutch pressure plate, i.e. a clutch driven element with the clutch drive element rotatively restricts the rotary displacement of the engine relative to a torque converter output element, eliminating the slip within an automatic transmission torque converter.
The clutch driven element is rotatively connected through intermediate elements to the turbine of the torque converter and to the output element of the torque converter, both of which are rotatively fixed to one another. One of the intermediate elements connecting the clutch driven element with the output element is a set of springs which compress to allow the clutch driven element to be rotatively displaced relative to the turbine and the torque converter output element. Spring compression occurs upon engagement of the clutch driven element with the clutch drive element when they are rotating at different speeds or when the clutch is engaged and subjected to transient torsional impulses, such as impulses produced by the engine firing frequency. When displacement between the elements occurs because of either clutch engagement or the transmission of transient impulses, the driveline system, comprising the elements rotatively connected to the clutch driven element, may respond by rotatively vibrating at a natural frequency associated with the system.
Driveline systems have a number of modes of vibration, each mode with its own natural frequency. It is desirable to minimize the amplitude of the vibrations produced by these vibration modes. A common method of minimizing and reducing the magnitude of the vibrations is to apply a rotary frictional load between the clutch driven element and the torque converter output element, in parallel with the spring force. Another method is to provide a viscous load between the clutch driven element and the torque converter output element. The result with either method is to damp out the vibrations between the clutch driven element and the torque converter output element.
Those damping methods may not be adequate when the frequency of the exciting force is at a natural frequency of the system. When the initial amplitude of the exciting force is sufficient to overcome the frictional or viscous resistance, and the exciting force is at a natural frequency, then the sympathetic elements of the driveline system will oscillate at an amplitude sufficiently large to become objectionable to the vehicle operator in the form of noise and vibrations transmitted through the structure of the vehicle.
The use of tuned propeller shaft dampers, the dampers comprising a ring shaped inertia element with a layer of rubber between the ring shaped inertia element and the propeller shaft, would not be effective in quieting these vibrations in the driveline system of a rear drive vehicle. Such a damper is beneficial only to the extent that reducing propeller shaft vibration reduces overall system vibration. In systems where the sympathetic element is being excited by the engine firing frequency and is on the input side of the transmission, a propeller shaft vibration damper would only be effective in damping the vibrations of those elements in a single gear ratio.